Well-heads for hydrocarbons and auxiliary exploitation and maintenance arrangement



Dec. 26, 1967 H. A. MARION l 3,360,042

WELL-HEADS FOR HYDROCARBONS AND AUXILIARY EXPLOITATION AND MAINTENANCEARRANGEMENT v Filed March 9, 1965 v 4 Sheets-Sheet 1 Dec. 26, 1967 H. A.MARION WELL-HEADS FOR HYDROCARBONS AND AUXILIARY EXPLOITATION FiledMarch 9, 1965 AND MAINTENANCE ARRANGEMENT 4 sheets-sheet :av

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'1167/ msw TATION Dec. 26, 1967 H. A. MARION WELLf-HEADS FORHYDROCARBONS AND AUXILIARY EXPLOI AND MAINTENANCE ARRANGEMENT FiledMarch 9, 1965 4 Sheets-Sheet 3 Dec. 26, 1967 H. A. MARION WELL-HEADS FORHYDROCARBONS AND AUXILIARY EXPLOlTATION AND MAINTENANCE ARRANGEMENTFiled March 9, 1965 4 Sheets-Sheet 4' United States Patent O WELL-HEADSFOR HYDROCARBONS AND AUX- ILIARY EXPLOITATION AND MAINTENANCEARRANGEMENT Henri Albert Marion, Rueil-Malmaison, France, assignor toSociete dEtude du Transport et de la Valorisation des Gaz Naturels duSahara S.E.G.A.N.S., Paris, France, a French corporation Filed Mar. 9,1965, Ser. No. 438,302 Claims priority, application France, Mar. 14,1964, 967,471; Feb. 24, 1965, 6,777

` 13 Claims. (Cl. 166-.6)

ABSTRACT F THE DISCLOSURE An underwater oil well comprising a productiontu-be carrying a well-head connected to a Christmas tree by a releasablequick-action remotely controlled connection, a lateral guiding systemfor the Christmas tree between the lowermost and a raised positionthereof, and hollow ballast means connected to the Christmas tree andadapted to be put in communication with a source of compressed air or asource of liquid for raising or lowering the Christmas tree relative tothe Well-head.

The invention relates to wells which are sunk in a region covered withwater and more particularly to wells for extraction of mineral oil sunkin coastal regions or under a lake, at depths at which the maintenanceof the well can no longer be effected by means of independent divers.This limit is actually less than 100 meters and the diiculties ofextraction rather than those of sinking prevent the sinking of deeperwells. The invention also relates to wells with shaft heads at a depthless than that specified above. v

The invention has-the object of providing an arrangement permitting theraising of the production tube, the Christmas tree, and the ends of thedistributor conduits connected thereto, to a shallow zone including Ithesurface, where divers can carry out effective maintenance work andsubsequently put the well back into production.

Substantially, the invention consists in combining an improved Christmastree with a lateral guide system therefor in the submerged and raisedpositions, and sealing means surrounding the production tube, the outerends of which are smooth. The bottom end of the Christmas tree has aquick-action connection to the Well head, such as is known in the art,and is integral with at least one ballast tank connected by a controlconduit to a iioat near the surface. A control vessel recovers this oatand after connecting compressor-s to the control conduit, it can supplycompressed air to the system, whereby the Christmas tree which waspreviously connected with the head, is disconnected therefrom and may begradually raisedtogether with the production tube and the ends of thedistributing conduits. The gradual filling of the ballast tank or tanksby a liquid, such as water, makes it possible to reverse this operationfor placing the Christmas tree into position after the maintenancetherefor or of the well base.

According to a preferred embodiment of the invention, two differentballast tanks serve respectively for the unlocking and lifting of theChristmas tree and its acces- 3,360,042 Patented Dec. 2 6, 1967 ICCsories. Moreover, these ballast tanks are symmetrical relative to theaxis and of ring shape.

According to another feature of the invention, the raising meanscomprise a submergible vessel -carrying divers. These means are capable,in shallow depths of resting on the ground underwater immediately-adjacent to the well head and permitting the -divers to carry out theirwork on the well heads and their accessories, and are equipped, for workin greater depths, with means for attaching the raising means to thewell head there being provided a device for unlocking and raising thewells, the vessel remaining fixed to the head during the raising andduring the return of the well head to the assembled position on theunderwater bottom so as to -guide the vertical movement of the -wellhead, the said underwater vessel -being moved in the vertical plane byacting on the ballast means therefor and acting merely as guide duringthe rising or descending movement of the head a full stop.

The vessel comprises a `device for effecting a certain number ofreconditioning operations (workover) The invention will be furtherdescribed, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 is a diagrammatical side elevation and shows the raised andsubmerged state of the device according to the invention;

FIG. 2 is a partial cross-section taken along the median plane of amineral oil well equipped with such an arrangement;

FIG. 3 isan axial cross-section of al submerged well head and itsaccessories and the hull ofasubmergib-le vessel, attached and locked tothe well head;

FIG. 4 is a detail of FIG. 3 and shows the iixing means fixing thevessel to the well head;

FIG. 5 is a cross-section along the line 5 5 in FIG. 3; v

FIG. 6 is a cross-section along the line 6 6 in FIG,

FIG. 7 is an axial cross-section on a larger scale of a union betweentwo conduits according to another feature of the invention;

FIG. 8 is a cross-section along the line 8-8 in FIG. 7;

FIG. 9 is a perspective view of a half-union, showing the arrangementfor locking the jacks; and

FIG. `10 shows diagrammatically the hull of a submergible vesselequipped with a diving bell mounted on a platform on which is locatedthe shaft head.

The drawings show a mineral oil well, the depth of which is naturallynot shown to scale and which comprises in the usual manner a casing 1a,1b, 1c, externally cemented together, the different parts being retainedtogether by a suspension arrangement 2a, 3b; 2b, 3c. Reference numerals3b, 3c signify hangers which rest on supports 2a, -2b. The latter may`be integral with bayonet locks, the top one of which is integral inturn with the actual well head 4.

The well head 4 has in its upper part a conical guide 6 and an annularshoulder 8 serving for mounting a connection 7 integral with a Christmastree or `distributor 15. This connection comprises, as known in the art,several latches 9, and external centering housing 7a which cooperateswith the guide 6 of the shaft head, 'and an annular double-acting,hydraulic piston 10 which actuates and locks the latches 9 when in thelowest position. Connected to this piston are several rods 11, integralat their other ends with a ballast tank 12 which is symmetrical relativeto the axis of the shaft, and has, for example, a ring shape.

The housing 7a may be fixed by means of struts 13 to a further ballasttank 14, also of ring shape. A plurality of conduits 26 connect thisballast tank with a oat 27 immersed at a sufficient distance from thesurface to avoid any damage thereto by surface traffic. Cables or chains116 connect the connection 7 to stationary members or weights 18arranged on the bed symmetrically, relative to the well head assembly 2.These cables may be equipped with a ballast 17. Conduits 19, forming thedistributing network and either submerged or located on the surface leadto the Christmas tree 15. They may be supported by means of oats 20distributed over the region where these conduits are subjected tomaximum exions.

A production tube 21, mounted at its top end by any known means on theChristmas tree 15, is smooth in its upper part and equipped for thispurpose with threaded connectors 2lb which differ from the conventionalconnectors 21a. At its lower end, it has an intake 24 which passesthrough one or more sets of seals or packers 22 of conventional type,which have a non-return valve 23. The seal between the intake end 24 andthe packer or packers 22 may be effected by a plurality of seals 25mounted on the intake end 24. As shown in the drawing, the seal of theupper end of the production tube is effected by means of severalconventional seals 5, for ex ample by several superimposed seals havingannular lip portions.

The upper part of the Christmas tree 15 may also be equipped with aconical flange 6a and a shoulder 8a, for attaching any desired auxiliaryequipment, which may be guided by cables fixed to the members 13, up tothe surface, if this is required.

The device hereinbefore described operates as follows:

At the end of the drilling, when the casing assembly 1a, 1b, 1c is inplace and suspended from the flanges 2a, 2b, one or more packers 22equipped with non-return valves 23, are lowered into the lowermost tube1c. Then the production tube 21 is placed into position, passing throughthe head via a plurality of seals. Then the well is completed bylowering the Christmas tree 15, connected with the distributing conduits19, from which the production tube is suspended. The production isremotely controlled by conventional means, for example, by means ofhydraulic valves, the control circuits of which extend along theconduits leading to the ballast tank.

The workshop ship drilling and finishing the wells can now travel toanother well and the oats 27 which oat at a small depth beneath thesurface facilitate the finding and the control of the well head inproduction.

When this well is to be maintained or repaired, the workshop vesselreturns and locates the immersed fioat 27, e.g., by means of ultrasonicdetectors. The vessel is positioned above the well and divers connectthe cornpressed air conduit 27 to compressors on board the vessel. Thecompressed air supplied to the :ballast tank 12 results in a sufiicienttractive force to lift the annular piston 10, if the hydraulic actuationof this piston has been ineffective, and the latches 9 release theshoulder` 8 of the well head 4. The forcing of compressed air into theballast tank 14 results in sufficient upward force to lift the assemblyformed by the Christmas tree 15, the conduits 19, the connection 7, theguide cables 16 and the production tube 21. The upper part of the tube21 slides through the seals and intake end portion 24 travels throughthe packers 22, whilst the seal of the lower part of the tube iseffected by means of seals 25. The lifting height ymay -be such that theintake end 24 leaves completely the lowermost packer whose non-returnvalve closes immediately under the action of the pressure and of aspring with which it is equipped. The flexibility of the conduits net 19and of the cables 16 is sufficient in view of the small displacement ofthe Christmas tree in the vertical direction to enable them to reach thesurface from their horizontal position.

The forces involved are the following:

The apparent weight a of the production tube.

The apparent weight b of the Christmas tree 15 and its accessories:connection 7-11 and ballast tank 14 (b may be in the upward or downwarddirection according to the contents ofthe ballast tank) The apparentweight c of the guide assembly 16, 17 in the lifted position.

The differential thrust d of the water and mineral oil on thecross-section of the production tube.

The unlocking effort e exerted by the ballast tank 12 on the rods 11.

The frictional forces f on the lateral wall of the production tube 21.

It is now possible to describe the conditions with these various forces.A11 axis directed towards the bottom is chosen and it is assumed thatthe differential thrust d is exerted only in the lowermost position. Theclosure of the valves 23 of the packers 22 cancels this pressure fromthe start of the lifting of the production tube 21. In the low position,the apparent weight c of the guide assembly is affected by a coefficientk which is less than unity.

The equilibrium at the surface is:

during the lifting, since the friction f has the same signa-l-b-t-kc-l-d--o (d is generally negative) during the lifting, sincefhas the same sign as a:

b -(a+kC-l-f+d) during the descent, f having changed its sign b fakcd(4) In the case of a 3000 meter well drilled on a bed or floor 300meters deep with a 4" production tube and a pressure at the well head of230 kg./cm.2, it follows:

a=l60 tons, c=l10 t., d=vl6 t., f=i20 t., and e=4 tons, taking intoconsideration a safety factor for the unlocking; k=1/10.

It may be seen that the oatability of the ballast tank is determined bythe inequalities (l) and (4), the value being in this example 65 tons,which is an easily obtainable value.

If a single ballast tank 12 is used, connected to the rods 11, it isobvious that the effort for lifting is much larger than that forunlocking. If not, the oatability of the auxiliary ballast tank 12 isdetermined by the unlocking force e. f

Obviously it is desirable that the effort for lowering resulting fromfilling the ballast tank 14, should be less than the ultimate strengthof the produtcion tube in respect of buckling.

Under these conditions, the arrangement of the invention permits therepeated lifting of the production-tube, and thus a variety ofoperations which are normally irnpossible with a submerged well(maintenance oflvalves, servicing of the tube by cables, maintenance ofthe shaft by a land-type snubbing unit, injections of acid, mud orcement, fracturing operations, and generally any operation connectedwith the exploitation and maintenance covered by the general termservicing).

The raising can be effected by means of the improved arrangement shownin FIGS. 3-9.

According to the embodiment illustrated in FIGS. 3-9, the well headassembly T (shown by the dash-dot lines) is surrounded at a suitabledistance by an annular casing 101 whose base is conveniently ballastedand anchored .on the underwater bed or oor. This casing 101 may serve onthe one hand as protection for the head assembly against water currentsand on the other hand as support for the conduits 19 which are mountedby known means on the casing, for example, by a system of collars orflanges, 102.

Apart from these parts, the well head has an upper part 103 with a cover104 of externally cylindrical shape above its Christmas tree this coveris mounted on the well head by suitable means, e.g., by bolting (notshown).

Machined in this cover 104 is a preferably conical aperture 105 whichextends into a cylindrical portion 105 and a circular recess or chamber107 (FIG. 4) and terminates in a cavity 108 which is also conical.

At the bottom of the cavity 108 is an aperture 109 equipped with avalve, not shown, which replaces the compressed air inlet 27 and thepipelines 26 for supplying compressed air to the ballast tanks 12 and14, as shown in FIG. .2.

A submergible vessel, shown diagrammatically at 110 is formed integrallywith a hollow rod 111 via a member 112 o-f the vessel 110; this rod 111terminates at its lower end in a male conical nozzle 113. The rod isequipped with a locking arrangement 114, and the arrangement isactuated, for example hydraulically, by jacks controlling the keying ofthe rod 111 in the recess 107, as in FIG. 4, as well as the unkeying ofthe rod.

A tubular sleeve 115 with two conduits 115a and 115b is adapted to slidein the rod 111 under the action of a jack (not shown). This slidingaction connects the conduits 115a, 115b with a valve box 118, connectedto a conduit 119. Another valve box 120 connects the conduit 119 withducts 116, 117.

In order to enable several control `operations to Abe carried out on thewell head, control members, described hereunder are provided.

The network of conduits 19 of the well head comprises the Christmas tree15 connected to the conduits 19 through a circular collector 121 whichrests on the annular casing 101. The collector is connected to theChristmas tree by one or more pipes 122 which form part of the well headassembly and comprise a part, not shown, permitting a slight slidingaction along the pipes 122, such as a flexible joint.

Each pipe 122 terminates adjacent the collector 121 in a valve 123; theconnection with the collector 121 is made by a union arrangement 124 anda second valve 125. The union arrangement is of special construction andshown in FIGS. 7, 8 and 9.

The valves 123, 125 may be of any suitable type, adapted for underwateruse. Preferably they are Iof the stopcock type with integral passage,while the seats of the valves may be self-lubricating. Opening andclosing may be effected by means known in the art, for example, byrotating through a quarter turn a spindle carrying a rotating key, thespindle itself being controlled from the underwater vessel 110.

The valves 123, 125 and other controls are controlled from a controlplatform 126. As shown in FIG. 5, this platform may be circular, but itmay also be a rim of light construction or a crown concentric with theaxis of the rod 111 having sectors in the form of radial spokes. Theremote control means, such as 127, 128, 129, 130 are fixed radially `onthis platform 126.

The platform may be moved vertically relative to the vessel 110 by meansof a ring of vertical jacks 131, for

6 example hydraulically controlled. The heads of the jacks 132 are fixedrigidly on a base 133 of the -vessel 110 and their bases are verticallyfixed with the platform 126, by means of an assembly shown generally at135 (FIG. 3).

This locked assembly comprises circular members 134a which have acircular recess 136 sliding in a groove having annular edges 137, 138,and are concentric relative to the tubular sleeve 115. The edges 137,138 form part of the platform 126. The outer edge is equipped with atoothed ring or rack 139 mating with pinions 140, mounted on shafts ofelectric motors 141 located in the jacks 131.

It will be understood that the platform 126 may he subjected to twomovements, namely:

(a) a rotational movement about'the axis of the sleeve 115 under theaction of the electric motors 141; (b) a vertical translatory movementunder the action of the jacks 131.

Each movement is limited by stops; the limits of the movements may beindicated by electric indicating means known in the art which producesignals on board the Vessel.

On the periphery of the platform 126 are projecting portions 142 (FIG.5) forming abutment surfaces 143 which may make contact withcorresponding abutments 144 on the annular casing 101. The platform 126is guided in its rotational movement by plastic rollers 145 or rollersof other suitable material which bear against a circular base formed onthe rod 111.

The vertical movement is limited by annular stops 147, 148 fixed,respectively, on the base 146 and .on the platform 126 and serving as anelectric signal contact.

The tools 127-130 mounted on the platform 126 control the valves 123,125, the connecting arrangement 124 and one or more control devices 149for controlling the output .of hydrocarbons by rotation of aconventional drum.

The tools 127, 129 and 130 control the valves 123, 125 and the outputcontrol device 149, previously equipped with tools in the form oftubular spanners or keys on their shaftsrEach tool comprises an electricmotor under a tight cover which controls the rotation of the shafts bymeans of the tubular keys and a suitable reduction gearing (not shown).Their positions may be controlled, for example, by electric contactsproducing a signal on the vessel 110. The connecting device 124 will nowbe described with reference to FIGURES 7-9.

This device 124 makes possible the connection of pipes such as pipe 122to the corresponding aperture of the ycollector 121 and comprises aconnecting head 151, formed integrally with the valve 123 and a hookmember 152 fixed to the valve 125. The connecting head is equipped withtwo jack half-collars 153, 154, one of said collars being provided in acircular end wall 155 of the connecting head 151 whereas the other isprovided in a half end wall 156. Extending through this head are waterconduits 157 connected to the jacks 153a, 154b for controlling them bypressurized water. A suitable seal 158 operating under Icompression ismounted in the end wall 155 to ensure a good seal between the two partsof the connection.

The hook member 152 comprises a circular end wall 159 and a half endwall 160 the shape of which is complementary to that of the connectinghead 151.

It is apparent from FIGS. 7 to 9 that the connection is made by loweringthe head 151 to the level of the hook member so that the end wall 159 ishooked behind the half end wall 156 and the end wall 155 behind the halfend wall 160. A sealing is achieved under the action of the jacks 153a,154a which exert a thrust against the end wall 159 and the half end wall160, Whilst crushing the seal 158 between the faces 161 and 162. Thejacks 153a, 154a are controlled by a control box 128, containing a pumpand the necessary valves for controlling these jacks through a conduit163 and a nozzle 164, also equipped with valves.

The unhooking of the pipes 122 from the collector 121 is effected byeliminating the pressure of the jacks 153s, 154g so that thecorresponding end walls of the head 151 and the member 152 are no longerpressed together and are released. A spring, not shown, may be providedbetween these parts to aid in the separation.

The operation of the lifting arrangement is as follows: Let it beassumed that a well head is at the bottom of the sea and must be workedover.

The underwater vessel 110 equipped with the rod 111 and the nozzle 113is lowered by introducing water into its ballast tanks. The approach'andengagement of the vessel can be supervised and controlled on one hand byultrasonic waves, and on the other hand by means of portholes andconventional projectors of submarine work suitably arranged on theunderwater vessel by means of a submarine television camrea mounted in asuitable position under the vessel.

During the descent, the conical nozzle, centered by the conical surface105, enters the cover 104. The nozzle passes through the cylindricalportion 106 and enters the cavity 10S. When the nozzle arrives at thebottom, an electric contact closes and produces a visual and/ or audiblesignal on the control panel of the vessel 110. Then the lockingarrangement 114 is actuated which keys the rod 111 in the recess 107. Inthis manner, a circuit is formed for supplying compressed air from thevessel 110 into the ballast tanks 12 and 14 of the well head through theconduits 115e, the valve assembly 113, the passage 119, the valve 120and the conduits 116, 117, by sliding the sleeve 115 in the rod 111under the action of a ram. Water is expelled from the ballast tanks 12and 14, causing the unlocking and then the raising of the well head.Previously, the pipe 122 was uncoupled from the collector 121 byactuating the connecting device 124 after closing the valves 123, 125.

The vessel 110 moves vertically under the effect of its own ballasttanks and remains fixed to the well head by the locking arrangement 114.

The vessel serves therefore as guide for the well head during its upwardmovement up to the operating level of the divers. These can leave thevessel through a port and carry out all maintenance work required on thewell head and on its accessories whilst the vessel 110 remains locked tothe cover 104.

Naturally, the raising can be continued until the well head reaches thesurface.

The maintenance and servicing of the well head having been finished, thewell head may be returned to its position on the sea bed by lling theballast tanks again with water through the conduits 115b disposed in thesleeve 115 and connected to the valves 118.

The vessel 110 descends with the well head under the action of its ownballast tanks and remains connected with the cover 104 due to thelocking arrangement 114 so that it guides the descent of the well head.

When the well head has reached the sea bed, the vessel 110 carries outthe reconnection of the well head to the collector 121 by means of theconnecting device 124; then the valves 123 and 125 can be opened.

Then the output of the network of conduits 19 is controlled by means ofthe tool 130 and the member 149.

When all reconditioning operations have been completed the vessel 110can be disconnected from the cover .104 by retracting the locking device114 by hydraulic action. The sleeve 115 is again raised in the rod 111and the vessel 110 can be moved to other submerged Well heads.

When the vessel 110 is locked on the cover 104, the

platform 126 can be positioned by rotation so as to cause the surface143 to abut the corresponding surfaces of the abutment members 144 sothat the tools on the platform are opposite the corresponding memberssuch as the valves 123, 125, the members 149 and the connecting device124. The abutment faces are equipped with suitable electric contactswhich produce signals on the control panel of the vessel 110 indicatingthe correct alignment of the platform 126 with the well head.

Then the jacks 131 are actuated in order to lower the platform 126vertically until the stops 147, 14S come to rest one on the other. Thecorrect vertical positioning is again signalled by electrical means.These positioning movements may be supervised and controlled, forexample, by underwater television.

The positions of the valves 123, 125 may be controlled, for example, bymeans of a plate fixed to the outside of each valve body, each platehaving two phosphorescent markings corresponding to the open and closedposition 0f the valve, while the spindle of each valve has also aphosphorescent lug which is aligned with one of the two markingsaccording to whether the valve is open or closed. Supervision is againby underwater television.

Any other control apparatus, such as an ultrasonic acoustic system canalso be used, wherein each valve position controls a transducer, theemission frequencies being diferent for each of the two positions of thevalve, and the supply circuit of the transducer being closed when thetool controlling the valve is placed in position.

The control of the position of the member 149 may again be effected by.any suitable means, for example, by a fixed sector with phosphorescentmarkings and a phosphorescent pointer which is mounted on the spindle ofthe member 149 and moves relative to the sector when the output of themember 149 is adjusted supervision being by underwater television.

The submerged well heads may thus be serviced by means of an underwatervessel according to the invention. Moreover, in the case of .a failureof the ballast tanks 12 and 14 of the well head, the vessel is capableof lifting the same by means of the upward thrust its own ballast tanksafter locking the vessel to the head, disconnecting the network ofconduits 19 and closing the valves.

The invention is not limited to the embodiment hereinbefore describedmerely by way of example.

In particular, the submergible vessel can be fixed to a well head whichis not adapted to be raised and the workover effected in this positionwhile the vessel remains at the bottom.

According to another modification of the invention which Acouldcorrespond to the case of a failure of the ballast tanks 12 and 14 ofthe well head T, or to a well head not adapted to be raised, these wellheads may be mounted on a base 165 (FIG. 10) which forms a platlform,the conduits 19 extending out of the side of this ase.

The vessel may be equipped for constant use or for given inspectionswith a skirt 166 which forms a diving bell and is connected to the hullof the vessel 110 by a conduit 167.

The vessel is seated on the platform by means of a guide socket 168,which may, for example, be conical Iand forms part of the platform 165.The well head and its accessories are thus enclosed Within the divingbell surrounding them and compressed air supplied by the vessel 110transforms the bell 166 into a diving bell. The divers, after gettingaccustomed to the required pressure by stages enter the bell through theport 167 under the vessel 110 and carry out the necessary work. Afterthe completion of the work, the divers re-enter the vessel 110 and,after the gradual reduction in the pressure, the vessel can move off toother well heads in order t-o carry out the required maintenance work.

I claim:

1. An oil well structure for oil production from an earth formationunder a body of water, said well structure comprising in combination awell casing, a well head, a Christmas tree carrying at its base areleasable connecting means connecting said Christmas tree to saidWellhead, a production tube to which said Christmas tree is xed, saidChristmas tree having hollow ballast means connected thereto, anunderwater vessel capable of carrying independent divers and includingfor work .at great depth releasable means attaching the vessel to saidChristmas tree, means putting the hollow ballast means selectively incommunication with a source of compressed air and a source of liquid,whereby said Christmas tree is raisable from said well-head by supplyingcompressed air to said ballast means, and lowerable to said well-head bysupplying liquid to said ballast means, the vessel remaining attached tothe Christmas tree during said raising and during the lowering of theChristmas tree so as to laterally guide the Christmas tree in thevertical movement thereof the vessel having and being vertically movableby hollow ballast tank-s combined therewith and acting merely as a guidefor the Christmas tree.

2. A well structure as claimed in claim 1, wherein the said Christmastree comprises a cover structure carrying conduits for putting saidballast means -selectively in communication with said source ofcompressed air and said source of liquid, said attaching means attachingthe vessel to said cover structure.

3. A well structure as claimed in claim 1, wherein the said underwatervessel is equipped with positioning means enabling it to position itselfrelative to the well head, said releasable means attaching the vessel tothe Christmas tree comprising two interengaging frustoconical guidemembers and locking means for selectively locking and unlocking said twoguide members.

4. A well structure as claimed in claim l, wherein the well head ismounted on a foundation forming a platform on said earth formation, -adiving bell which forms part of the said vessel resting on saidplatform.

5. A well structure as claimed in claim 1, wherein said Christmas treecomprises a plurality of oil collecting conduits radially extendingtherefrom and a ring-shaped manifold interconnecting said collectingconduits and coaxial with said Christmas tree, an annular sleeve coaxialwith said well head and supporting said manifold and adapted to besecured to said earth formation.

6. A well structure as claimed in claim 5, comprising a tool-carryingplatform which is carried by said vessel and rotatable and verticallymovable relative to said vessel by control means and carries toolsreleasably engaging control devices of said Christmas tree andreleasable means interconnecting said platform and said sleeve.

7. A well structure as claimed in claim 5, wherein each of saidcollecting conduits has an oil output regulating means, the connectionbetween the manifold and that part of each collecting conduit adjacentsaid Christmas tree comprising two remote-controlled valves and aremotecontrolled releasable connecting device interconnecting saidvalves.

8. A well structure as claimed in claim 7, wherein the said connectingdevice comprises a connecting head, a hook member engaging saidconnecting head, a releasable clamping device clamping said connectinghead to said hook member and sealing means between said connecting headand said hook member.

9. An oil well structure for oil production from an earth formationunder a body of water, said well structure comprising in combination awell casing, a well-head, a Christmas tree, a releasable connectionmeans interconnecting said Christmas tree and said well-head andcomprising an upwardly movable member for releasing said connectionmeans and disconnecting said Christmas tree from said well-head, lateralguide means connected to said Christmas tree for the guiding thereof inmovements between a lowermost position adjacent said wellhead and anupper position in which work to be carried out on said Christmas tree isfacilitated, an oil production tube connected to and depending from saidChristmas tree into said well casing, hollow ballast means connected tosaid Christmas tree and said releasing member, means for supplyingliquid to the interior of said ballast means, conduit means connected toand extending upwardly from said ballast means and having an upper endfor connection to a source of compressed air, and iioat means connectedto said conduit means adjacent said upper end thereof for maintainingsaid upper end at a desired level in said body of water, whereby saidChristmas tree can be disconnected from said well-head and raised insaid body of water by supplying compressed air to said ballast means byway of said conduit means and lowered to said well-head by allowing saidliquid to enter said ballast means.

10. A well structure as claimed in claim 9, wherein the lateral guidemeans comprises a plurality of cables connected to and radiallyextending from the Chri-Stmas tree, the cables being substantially tautand having ends remote from the Christmas tree connected to said earthformation, the lateral guide means having suicient ilexibility to allowsaid movements of the Christmas tree.

11. A well structure as claimed in claim 9, wherein said ballast meanscomprise a ballast tank for said releasing member which is separate froman upwardly movable relative to a ballast tank connected to saidChristmas tree.

12. An oil well structure for oil production from an earth formationunder a body of water, said well structure comprising in combination aWell casing, a well-head, a Christmas tree, a releasable connectionmeans interconnecting said well-head and said Christmas tree, means forreleasing said connection means, guide means associated with saidChristmas tree for the guiding thereof in movements between a lowermostposition adjacent said well-head and an upper position in which work tobe carried out on said Christmas tree is facilitated, an oil productiontube connected to and depending from said Christmas tree into said wellcasing, hollow ballast means connected to said Christmas tree, saidballast means being adapted to be put selectively in communication witha source of compressed air and a source of liquid whereby said Christmastree is selectively raisable to said upper position by said ballastmeans after release of said connection means and supply of compressedair to said ballast means and lower-able to said lowermost position bysupplying liquid to said ballast means.

13. An oil well structure for oil production from an earth formationunder a body of water, said well structure comprising in combination awell casing, a wellhead, a Christmas tree, a quick-action releasableconnection means interconnecting said well-head and said Christmas tree,a control element upwardly movable relative to said Christmas tree andcombined with said connection means for releasing said connection means,a first ballast tank connected to said control element, guide meansassociated with said Christmas tree for the guiding thereof in movementsbetween a lowermost position adjacent said well-head and an upperposition in which work to be carried out on said Christmas tree isfacilitated, an oil production tube connected to and depending from saidChristmas tree into said well casing, a second ballast tank connected tosaid Christmas tree, said ballast tanks being adapted to be connectedselectively to a source of compressed air and a source of liquid wherebysaid Christmas tree is selectively raisable relative to said Well-headby supplying compressed air to said first ballast tank to release saidconnection means and to said second ballast tank and lowerable bysupplying liquid to said ballast tanks.

(References on following page) 1 1 1 2 References Cited 3,186,486 6/1965 Rhodes et al. 166-.5 3,221,816 12/1965 Shatto et a1 166-.5 UNTTEDSTATES PATENTS 3,256,937 6/1966 Haeber et a1. 16e-.6

6/1950 Tucker 175-8 X 1/ 1962 Rhodes et al. 175-7 5 FOREIGN PATENTS11/1962 Baller et aL 1166-15 8741 8 1 1 B 12/1964 Dudley. 7 8/ 96 Great`rxtam. 1% gsttlf et a1. g-.g CHARLES E. OCONNELL, prima@ Examiner.

a ms 2/1965 Brown 166-48 lo JACOB L. NACKENOFF, Exanine. 4/1965 Haeber166-.5 RICHARD E. FAVREAU, Assistant Examiner.

12. AN OIL WELL STRUCTURE FOR OIL PRODUCTION FROM AN EARTH FORMATIONUNDER A BODY OF WATER, SAID WELL STRUCTURE COMPRISING IN COMBINATION AWELL CASING, A WELL-HEAD, A CHRISTMAS TREE, A RELEASABLE CONNECTIONMEANS INTERCONNECTING SAID WELL-HEAD AND SAID CHRISTMAS TREE, MEANS FORRELEASING SAID CONNECTION MEANS, GUIDE MEANS ASSOCIATED WITH SAIDCHRISTMAS TREE FOR THE GUIDING THEREOF IN MOVEMENTS BETWEEN A LOWERMOSTPOSITION ADJACENT SAID WELL-HEAD AND AN UPPER POSITION IN WHICH WORK TOBE CARRIED OUT ON SAID CHRISTMAS TREE IS FACILITATED, AN OIL PRODUCTIONTUBE CONNECTED TO AND DEPENDING FROM SAID CHRISTMAS TREE INTO SAID WELLCASING, HOLLOW BALLAST MEANS CONNECTED TO SAID CHRISTMAS TREE, SAIDBALLAST MEANS BEING ADAPTED TO BE PUT SELECTIVELY IN COMMUNICATION WITHA SOURCE OF COMPRESSED AIR AND A SOURCE OF LIQUID WHEREBY SAID CHRISTMASTREE IS SELECTIVELY RAISABLE TO SAID UPPER POSITION BY SAID BALLASTMEANS AFTER RELEASE OF SAID CONNECTION MEANS AND SUPPLY OF COMPRESSEDAIR TO SAID BALLAST MEANS AND LOWERABLE TO SAID LOWERMOST POSITION BYSUPPLYING LIQUID TO SAID BALLAST MEANS.